UGC NET Computer Science PYQ, June 2015 (Paper II & III, Selected Questions)

Explanation

S₁: Boolean expressions and logic networks correspond to labeled acyclic digraphs. S₂: Minimal expressions do not always give the simplest network. S₃: Greedy K-map grouping may not give an optimal expression. So S₁, S₂ and S₃ are all correct.

Explanation

For a full adder, S = A ⊕ B ⊕ Cᵢₙ and Cₒᵤₜ = A·B + Cᵢₙ·(A ⊕ B). (a) A = 1, B = 0, Cᵢₙ = 0: S = 1 ⊕ 0 ⊕ 0 = 1, Cₒᵤₜ = 1·0 + 0·(1 ⊕ 0) = 0. (b) A = 0, B = 1, Cᵢₙ = 1: S = 0 ⊕ 1 ⊕ 1 = 0, Cₒᵤₜ = 0·1 + 1·(0 ⊕ 1) = 1. So S = 1, C₀ = 0 and S = 0, C₀ = 1.

Explanation

S₁: (c ∧ b) → r S₂: ¬b → ¬p Conclusion: (¬r ∧ p) → ¬c So: if (c ∧ b) → r and ¬b → ¬p, then (¬r ∧ p) → ¬c.

Explanation

(a) Contrapositive: negate both hypothesis and conclusion and interchange them: (p → q) ⇔ (¬q → ¬p). (b) Exportation is a valid rule of replacement: ((p ∧ q) → r) ⇔ (p → (q → r)). (c) Reductio ad absurdum: (p → q) ⇔ [(p ∧ ¬q) → 0]. (d) Equivalence (biconditional): (p ↔ q) ⇔ (p → q) ∧ (q → p). So a-(i), b-(ii), c-(iii), d-(iv).

Explanation

The proposition is "if x² ≥ 25 then x ≥ 6", but the proof assumes x ≥ 6 and derives x² ≥ 25. So the proof starts by assuming what is to be shown and actually proves the converse; the proof is not correct. Statements (1) and (2) are correct, statement (3) is not.

Explanation

Message passing interface (MPI) is a standardized and portable message passing system. • It can run on any hardware platform. It is portable, efficient, flexible. • It has become a de facto standard for communication among memory system. • MPI – Comm. – Size returns the total number of MPI processes in specified communication. So answer is (c)

Explanation

Translator which performs macro calls expansion is called macro pre-processors

Explanation

Take the first node in preorder traversal a will be the root. Now we construct the binary tree Therefore, postorder is - debfgca

Explanation

Level order traversal is similar to breadth first search, whereas preorder traversal is similar to depth first search. So the answer is (a).

Explanation

The complexity is commonly estimated by counting the number of elementary operations performed by the algorithm, where an elementary operation takes a fixed amount of time to perform. Thus the amount of time taken and the number of elementary operations performed by the algorithm differ by at most a constant factor.

Explanation

Linear search runs in at worst linear time and make at most n comparisons, where n is the length of the list. If each element is equally likely to be searched then the linear search has an average case of (n/2) comparisons, but the average case can be affected if the search probability for each element vary.

Explanation

Radix sort because it sorts in integers in range 0 … (n² – 1) in O(n) time using base-n representation.

Explanation

Using Kruskal's algorithm: take 10 (1–6), 12 (3–4), 14 (2–7), 16 (2–3); skip 18 (4–7, cycle); take 22 (4–5); skip 24 (5–7, cycle); take 25 (5–6). Total = 10 + 12 + 14 + 16 + 22 + 25 = 99, which is option (b).

Explanation

Relational operators > and >= have higher precedence than ==, so the expression is (--x + j) == ((x > n) >= m). --x makes x = 6.5, so LHS = 6.5 + (–1.0) = 5.5. RHS: (6.5 > 1.0) = 1, then (1 >= 2.0) = 0. 5.5 == 0 is false, so the value is 0.

Explanation

S occupies addresses 1000 to 1008: A B C D E F G H \0. S[3] is 'D', and *(&S[3]) is 'D' itself, so %c prints D. S + 4 skips 4 characters, so %s prints "EFGH". %u prints the base address of S, 1000. Final output: DEFGH1000.

Explanation

Reference string 0 1 7 2 3 2 7 1 0 3 with 4 frames (LRU): 0, 1, 7, 2 are faults (4); 3 replaces 0 (5); 2, 7, 1 are hits; 0 replaces 3 (6); 3 replaces 2 (7). Total page faults = 7.

Explanation

Reading of two process won't create any problem, So answer is (c)

Explanation

By Amdahl's law, the serial part (1 – P) cannot be sped up while the parallel part P is divided among N processors, so the maximum speed-up is 1 / [(1 – P) + P/N].

Explanation

SSTF from cylinder 24: 24 → 26 (2) → 12 (14) → 8 (4) → 4 (4) → 42 (38) → 50 (8). Total distance = 70 cylinders. Seek time = 70 × 6 msec = 420 msec = 0.42 sec.

Explanation

The Unix Kernel maintains two key data structures related to processes, the process table and the user structure. In user structure there is no place for scheduling parameter process table store the information of all running process. The process table contains process ID's, memory usage of the process, what are file descriptor used in the process.

Explanation

Traditional file system has all mentioned drawbacks. Database applications built by using tables are used to overcome them. eg : Normalization and integrity constraints reduces redundancy & inconsistency. Select * from table provide easy access to data references, joins etc removes data is action primary & foreign key along with check predicates solves integrity problem

Explanation

Every weak entity must be associated with an identifying entity i.e. the weak entity set is said to be existence dependent on the identifying set. The identifying entity set is said to own the weak entity set that it identifies. It is also called owner entity set.

Explanation

If you drop child table first, the foreign key will be dropped as well. If you attempt to drop percent table first you will get an "could not drop object "a" because it is referenced by a foreign key constraint error, Drop table can not be used to drop a table reference by a foreign key constraint. The referencing foreign key constraint or the referencing table must be dropped.

Explanation

We have weak entities for several reasons : • We want to avoid the data duplication and consequent entity. Possible inconsistencies caused by duplicating the key of strong. • Weak entities be stored physically with their strong entities • Weak entities can be detected automatically when their strong entity is detected. So (d) is incorrect statement, Hence (d) is the answer.

Explanation

CREATE ASSERTION <assertion name> CHECK <predicate> is the proper syntax. For example, an assertion demanding that there is no more than one president among the employees: CREATE ASSERTION AT_MOST_ONE_PRESIDENT CHECK ((SELECT COUNT(*) FROM EMP e WHERE e.job = 'PRESIDENT') <= 1).

Explanation

In basic two-phase locking there is a chance of deadlock. The timestamp-ordering protocol ensures conflict serializability and, since no transaction waits, it is free from deadlock. So the answer is (2) only.

Explanation

Semantics of the information transmitted is not associated with the session layer but associated with presentation layer So correct option is (c).

Explanation

In class addressing : (1) the number of addresses needs to be power of 2 (2) The mask needs to be included in the address to define the block (3) The starting address must be divisible by the number of addresses in block So answer is (d)

Explanation

PVM provides fault tolerance through dynamic addition and deletion of hosts/processes, and message buffers are allocated dynamically. PVM guarantees that message order between any pair of tasks is preserved, so statement (d) is incorrect.

Explanation

Session initiation protocol is an application layer control protocol that can establish, modify & terminate multimedia sessions such as internet telephony calls.

Explanation

23 port number is (TELNET) that uses by remote login 25 port number is (SMTP) that uses by E-mail 80 port number is (HTTP) that uses by world wide web 119 port number is used by USENET news

Explanation

Total length 16 bit field define the entire packet size in IPv4, including header and data, in bytes. The minimum length packet is 20 bytes (20 byte header. + 0 byte data) and maximum is 65, 535 bytes the maximum value of a 16 bit word.

Explanation

The waterfall model was first process model to be introduce. • It is also referred as linear sequential life cycle model • It is very simple to understand and use. In this each phase must be complicated fully before the next phase can begin. • In this model the testing stands only after the development is complete • In this model phases do not overlap

Explanation

(a) Size oriented metrics is directly implied with (iii) (b) Function oriented metrics is number of user inputs, number of user outputs, number of files, number of external interfaces. So it satisfies (i) (c) Extended function point metrics is a superset of the function point measure that can be applied to system. It uses algorithm characteristics as one of the measurement parameter. (d) Function point is a "unit of measurement" to express the amount of business functionality an information provides to a user.

Explanation

Project planning means identifying the activities, milestones and deliverables produced by a project. It is commonly perceived as creating a Gantt chart, which is incorrect; a Gantt chart is merely a visual representation of the project schedule.

Explanation

A cohesion module performs a single task within a software procedure, requiring little interaction with little procedures in other parts of software. Type of cohesion : • A module that performs takes that are related logically is logically cohesion • When a module contains takes that are related by the fact that all must be executed with the same span of time, the exhibits temporal cohesion • At the low end of the spectrum, a module that performs a set of takes that relate to each other loosely called coincidentally cohesive.

Explanation

Validation is "Are we building the right product? According to the capability maturity model Software validation : The process of evaluating software during or at the end of the development process to determine whether it satisfies specified requirements.

Explanation

Inaccessible in the derived class, only public or protected members are inherited So answer is (a)

Explanation

Data members in C++ is inherited in a derived class from base class. Constructor is a member function of a class which initialize objects of a class. In C++, constructor is automatically called when object create. It is special member function of the class. Destructor is a member function which destructs or deletes an object. Virtual methods is a method which is redefined (over- ridden) in derived class.

Explanation

The first three statements are correct; the fourth is incorrect. Templates are more powerful and obey C++ syntactic rules, whereas macros do not, but templates take more compilation time and code size, so templates are not more efficient than macros.

Explanation

Data bits: d₈ = 0, d₇ = 0, d₆ = 1, d₅ = 1, d₄ = 1, d₃ = 0, d₂ = 0, d₁ = 1. Stored check bits p₈p₄p₂p₁ = 0111. Codeword layout (positions 12 to 1): d₈ d₇ d₆ d₅ p₈ d₄ d₃ d₂ p₄ d₁ p₂ p₁. Syndrome = 0111 XOR 1101 = 1010 = 10, so bit position 10, which holds d₆, is in error. Flipping d₆ gives the word that was read: 00011001.

Explanation

Given octal No. is (2550276)₈ = (010 101 101 000 010 111 110)₂ ⇒ (01 010 1101 0000 1011 1110)₂ ⇒ (0AD0BE)₁₆ (AD0BE)₁₆

Explanation

Remember with 'n' number of flip-flop you can get upto maximum modulo - (2ⁿ) counter. Since 2⁹ = 512 > 272 it can satisfy the condition.

Explanation

Since minimum bus cycle duration = 4 clock cycle bus clock = 8 MHZ then, maximum bus cycle rate = 8 m/4sec = 2m/sec Data transferred per bus cycle = 16 bit = 2 B Data transfer rate per second = bus cycle rate × data per bus cycle = 2 M × 2 = 4 × 10⁶ bytes/sec So, option (b) is correct.

Explanation

CPU speed is 1 MIPS = 10⁶ instructions per second. With programmed I/O, each byte transferred needs about one instruction-equivalent of 4 machine cycles (status check, branch, read/write data), so the maximum transfer rate = 10⁶ / 4 = 250,000 bytes/sec = 250 Kbytes/sec.

Explanation

Number of pointers that can be stored in the index block – which depends on the size of the index block and the size of each address. Size of each data block – because each pointer points to a block, so the larger the block size, the more data each pointer represents.

Explanation

The Floyd-Warshall algorithm solves the all-pairs shortest-paths problem efficiently in O(n³) time using dynamic programming.

Explanation

It will be solved by using branch and bound technique. The travelling salesman problem is NP- complete problem. It can also be solved by- one of the earliest application of dynamic programming is the Held-Karp algorithm to solve TSP in time O(n².2ⁿ).

Explanation

Branch and bound is an algorithm design paradigm for discrete and combinatorial optimization problems; it systematically enumerates candidate solutions by state space search. In branch and bound, the dynamic programming principle can be used to discard redundant partial paths.

Explanation

The golden rule in module design is to maximize cohesion and minimize coupling. Encapsulation is the key to implementing this rule.

Explanation

Interface: It is used to provide total abstraction. That means all the methods in interface are declared with empty body and are public and all fields are public, static and final default.

Explanation

An applet is a small program that is intended not to be run on its own, but rather to be embedded inside-another application.

Explanation

Processes are not permanently assigned to a queue they can vary between queues as their priorities change

Explanation

Memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passing through itself, primarily performing the translation of virtual memory addresses to physical addresses. It is usually implemented as part of the central processing unit (CPU), but it also can be in the form of a separate integrated circuit. So we can say it is a chip to map virtual address to physical address

Explanation

Just like linked list where insertion, deletion of blocks is easy. In linked allocation only pointer needs to be changed. In linked allocation each file is a linked list of disk blocks. The directory contains a pointer to the first block of the file, for example, a file of 5 blocks which starts at block 4, might continuous at block 7, then block 16, block 10, 8 finally block 27. Each block constrains a pointer to the next block & the last block contains a NIL-pointer. The value-1 may be used for NIL to differential it from block 0.

Explanation

Wow 32 is a running environment used in windows to run 16 bit windows application on a 32 bit machine

Explanation

You can edit more than one file at a time with vi. vi file1 file2 vi two (or more) files at the same time.

Explanation

A Unix file may be of any of the type like regular file, directory file, or device file.

Explanation

One table for each entity : 2 R₁ is one to many (No separate table): 0 R₂ is many to many and requires one separate table: 1 Total number of tables: 3

Explanation

The average marks of male students is more than the average marks of student in the university.

Explanation

Option (a) is which it is clearly mentioned that partial dependency exists is against 2NF principle. Question seems incomplete, because there is nothing said about functional dependency.

Explanation

Normalized device co-ordinates describe positions on a virtual plotting device: the lower left corner is (0,0) and the upper right corner is (1,1). NDC is a right-handed system, not left-handed, so statement (4) is incorrect.

Explanation

Circuit switching transmission technique guarantees the data packets will be received by the receiver in the same order in which they were sent by the sender because path is fixed and all packet goes through that path in same order.

Explanation

Key LAYER gives column order L = 3, A = 1, Y = 5, E = 2, R = 4. Writing the message row-wise: C O M P U T E R N E T W O R K Reading columns in order 1 (A), 2 (E), 3 (L), 4 (R), 5 (Y): OEW PNR CTT UEK MRO. Encrypted message: OEWPNRCTTUEKMRO.

Explanation

FIN control fields in TCP header is used to specify whether the sender has no more data to transmit i.e., close the connection from sender side.

Explanation

Transport mode:- IP header, IPSec, headers IP payload. Tunnel Mode:- New IP header, IPSec, headers, old IP header, IP payload. IP Sec can be implemented in a host-to-host transport mode, as well as in network tunning mode.

Explanation

The maximum payload of TCP segment is 65, 495 bytes. Because maximum IP packet is 65, 535 bytes out of which 20 is used for header. TCP header is 20 bytes. So, 2¹⁶ – 20 – 20 = 65535 – 40 = 65495 bytes left for TCP.

Explanation

Elicitation is the process of gathering, understanding and documenting requirement. Prioritization and negotiation are key activities within the elicitation process to ensure a feasible and well defined set of requirements for the project. Requirements Validation– This is the process of checking if the gathered requirements are correct, complete and consistent. Feasibility study– This is an assessment of whether a project is viable and achievable, considering factors like cost, resources and technology. Requirements Reviews– These are formal assessments of the requirements documentation, typically conducted by stakeholders and experts, to identify potential issues and ensure quality.

Explanation

We know our aim is to maximize cohesion & minimum coupling Strong form of cohesion is functional cohesion weakest form of coupling is data coupling.

Explanation

Adaptive maintenance is a modification of a software product performed after delivery to keep it usable in a changed or changing environment, e.g. porting the existing software to a new environment.

Explanation

In an XML DTD, + means one or more times, * means zero or more times and ? means zero or one time.

Explanation

In XML, DOCTYPE declaration can be used to define special characters & character string used in the document & it include a reference of document type definition file

Explanation

Refinement is surly a top down approach as we are extracting a particular type like person entity to s/w engineer. Refinement, process of elaboration, start with the statement of function defined at the abstract level, decompose the statement function in a step wise fashion until programming language statements are reached.

Explanation

The redundancy in images stems from pixel correlation. If the image is transformed to a representation where the pixels are decorrelated, the redundancy is eliminated and the image can be compressed.

Explanation

Since prolog is a dynamically typed language. Which is to say that programs are not checked for type errors until run time.